M3 adapter or Flashcart? confused here

hey all, im new to this homebrew stuff outside of my xbox, so my question is if I am looking to use have the ability to watch video, play mp3, and play eumlators on my DS, which should I go with.

It seems the M3 adapter is more expensive. Is that because it already comes with app's on it. If I want to use video, mp3, and emu's on my DS with a supercard flashcart and 1gig sd card, would I then have to put apps on to that?

Basically which one should I go with? and what are the advantages to the M3 adapter?
Thanks in advance